Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Electrocaloric effect materials are materials that can experience a temperature change when subjected to an applied voltage. This temperature change can be reversed upon the removal of the applied voltage. By physically coupling and decoupling electrocaloric effect material to and from a heat source, thermal energy can be dynamically transferred in quantities that are greater in one direction than the other. The described principles may be applied to a heat transfer device that can be utilized to transfer thermal energy away from a heat source.
The present disclosure appreciates that heat transfer devices utilizing electrocaloric effect materials may experience various performance limitations. Specifically, a heat transfer device utilizing conventional electrocaloric effect materials may experience a limited ability to concentrate thermal energy transferred away from a heat source. This performance limitation results from the configuration of a conventional heat transfer device that provides a fixed heat flux through the heat transfer device.
Heat flux may be described as the rate of thermal energy transfer per unit area of material through which the thermal energy is transferred. A heat transfer device may be configured to provide a particular heat flux depending on a number of factors, including but not limited to, the electrocaloric effect material characteristics of the electrocaloric effect material layers, thermal rectifier characteristics of the thermal rectifier layers, and the characteristics of the applied electrode control signal provided to activate the transfer of thermal energy through the heat transfer device. Irrespective of the heat flux designed for any particular heat transfer device, the heat flux is fixed across the length of that device, meaning the heat flux at the side of the device in thermal contact with a heat source is the same as the heat flux at the side of the device in thermal contact with a heat sink.
Heat pump applications exist in which it may be desirable to remove thermal energy from a heat source having a first surface area and heat flux and providing the thermal energy to a heat sink having a second surface area and heat flux that differs substantially from the first surface area and heat flux of the heat source. As an example, a refrigerator utilizes cooling coils that cool by removing heat at a low rate over a large space. Temperature changes within a refrigerator may be relatively mild. Accordingly, the heat flux associated with the cooling process may be low and spread over a large surface area. In contrast, a stove heats a burner very rapidly. The heat flux is high and is concentrated on a relatively small surface area. Although it may be desirable to utilize a heat transfer device that removes the thermal energy from the refrigerator and transfers that thermal energy to the stove to heat the burner, conventional heat transfer devices utilizing electrocaloric effect materials may not directly perform this function due to the fixed heat flux of the heat transfer device. If a heat transfer device having a high heat flux is utilized in this example, thermal energy would be transferred from too small of a space and at too high of a rate for continued operation of the refrigerator. If a heat transfer device having a low heat flux is utilized, thermal energy would be transferred too slowly over too large of an area to effectively heat the stove burner.